There exists a need to provide ergonomic support to workers using chairs to assist in decreasing fatigue, helping in the prevention of musculoskeletal disorders (MSDs), and related issues that result from pronged durations of time spent it a seated position. In the increasing sedentary environment of the modern workplace, recent trends emerged showing an increase in chronic medical problems, such as musculoskeletal disorders (MSDs) and an increase in worker fatigue arising when workers sit for prolonged durations of time performing tasks that require the worker to sit. These problems are, in part, due to the growing dependence on computers to perform tasks in offices and increasing levels of automation in the work place that reduce the amount of manual labor in the workplace. Over time, chair design has remained largely unchanged, by not providing for the differing needs of office workers.
The negative impact of inadequate ergonomic support provided to workers during extended time periods of seating manifests primarily in two ways. The first is an increased load on the health care system, typically due to an increase in MSDs and similar ailments. The second significant impact is a loss of worker productivity through lowered worker efficiency related to loss of concentration and absenteeism in connection with the treatment of MSDs or related ailments. Additionally, extended time periods of sitting without beneficial ergonomic support leads to a decrease in efficiency once a worker becomes fatigued. Fatigue due to extended time periods of sitting can cause the worker to take more frequent breaks effectively spending less time performing work, a higher incidence of work errors, and decline in worker attitude, all combining to drive up the cost of labor to the employer. Additionally, with an aging work force, employers will likely experience additional heath benefit costs as older workers become more prone to MSDs and other ailments. These relatively large costs can be circumvented through preventative steps taken by the employer to help reduce the number of MSDs and other ailments in the workplace due to inadequate ergonomic support of workers, as well as increasing the productivity of workers. These preventive measures may include proactive steps such as stretching and other therapeutic activities in the workplace. However, reliance on such proactive steps alone is insufficient. It is difficult to ensure employees participate in such proactive measures, and it may prove difficult to encourage such behavior. As a result, providing workers with ergonomic chairs capable of passively assisting the workers from becoming prone to MSDs, other related ailments, and fatigue is preferable. The relatively small investment of properly designed chairs will allow passive assistance to the worker to combat the aforementioned emerging health problems of the modern office environment.
The prior art recognizes the problems of workplace fatigue and chronic injury related to prolonged time periods of sitting. The prior art employs a variety of techniques in an attempt to assist in alleviating seating fatigue and helping to prevent the onset of MSDs and other related ailments. The use of a contoured back structure combined with an adjustment mechanism is a common attempted solution in the prior art. However, the use of a back pad in conjunction with a means of adjustment presents difficulty in assisting workers in overcoming undesirable ergonomic conditions associated with extended time periods of sitting. First, the adjustment mechanism can be complicated to operate. Moreover, the adjustment mechanism presents a potential failure point in that the adjustment mechanism may break preventing adjustments from being made. Also, the range of adjustment may allow the worker to adjust the back into a position that may be comfortable temporarily, but after continuous use lead to fatigue. This requires the worker to either continually adjust the back, or alternatively, adjust the back to a comfortable starting position and continue to work despite the onset of fatigue, precursors to MSDs, or other related ailments. Adjustable back designs may also lead to an impediment of the full range of motion of the seated worker while performing job tasks. Furthermore, chairs are commonly too big or too small for the worker using them, leading to inappropriate sitting positions that can cause fatigue also.
An example of a prior art solution employing an adjustable seat back is in U.S. Pat. No. 6,394,547 B1 to Vik, that discloses a seat back support that is positioned between the 2nd lumbar and the 11th thoracic vertebrae of the worker. The seat back in Vik provides a horizontal and vertical component of force normal to the workers' back that acts upon the worker's back. Vik attempts to provide a simple and inexpensive ergonomic chair that provides adequate support to a worker even when the worker leans back in the chair. Vik accomplishes this end by employing an adjustable back affixed in a cantilever fashion to a seat that is positioned between the 2nd lumbar and the 11th thoracic vertebrae of the worker. While Vik accomplishes providing the worker with back support, Vik fails to teach a dimensional relationship between the back, hips, and legs of the worker. Moreover, Vik does not address any problems related to the seat of the chair, nor does Vik provide any assistance in alleviating MSDs or other ailments related to the soft tissue of the worker's legs and posterior. Also, because Vik targets a specific region of the back, and the design explicitly requires that the back pad contact the worker at a specific location, workers may either be unfamiliar with where to position the back pad, or find the position uncomfortable and fail to use the pad correctly.
Further, a prior art example that includes an adjustable backrest is U.S. Pat. No. 5,624,158 to Adat et. al., that discloses a seat backrest that is adjustable in vertical height and contour in both the curvature of upper and lower portions of the backrest. Additionally, Adat et. al. provides adjustable lateral support to the worker. Adat et. al does recognize the need to provide freedom of movement in the worker's upper body; however, the adjustment mechanisms in Adat et. al. are complicated and involves several adjustment points, as well as several mechanisms for adjustment. The various mechanical adjustment structure in Adat et. al. are all prone to unreliability issues after repeated use. While Adat et. al. provides a plurality of adjustments to the worker, Adat et. al. also presents difficulty in that the worker must spend time fine tuning the adjustment at various points to achieve a comfortable backrest position. Note that Adat et al., has no criterion disclosed as to set the various backrest adjustments for specific issues related to extended sitting fatigue and discomfort.
Similarly, in U.S. Pat. No. 6,626,494 B2 to Yoo, a chair is disclosed with an adjustable backrest assembly that is adjusted by the worker to a desired position. However, there is no limitation on the adjustment to the backrest in Yoo, making the backrest infinitely adjustable. This could lead to continual adjustments by the worker, tending to prevent correct positioning. Moreover, because the worker can be unfamiliar with what backrest position is necessary to correctly align the spine, Yoo presents an opportunity for the worker to adjust the chair backrest into a less desirable or possibly detrimental position. Without supervision by a person qualified to determine the correct orthopedic position of the chair, Yoo does not solve the need to provide ergonomic support.
A further prior art reference that attempts to simplify the adjustment of the chair backrest is U.S. Pat. No. 7,147,282 B2 to Hatcher et. al., that incorporates the adjustment structure into the backrest support structure. Hatcher et. al. allows adjustments to be made by the worker without having to awkwardly reach behind or underneath the worker to make adjustments to the chair backrest. As Hatcher et. al. only provides backrest depth adjustment with respect to the seat, the issues of multiple adjustments with multiple potential reliability issues is solved, however the need still exists to correctly position the lower body of the worker to the chair backrest. Further, in Hatcher et al., there is no method disclosed on how to set the various adjustments of the backrest for specific MSD disorder issues from prolonged sitting.
Similarly, in U.S. Pat. No. 6,938,956 B1 to Piretti discloses a double backrest support structure for a chair with the desired solution of proper back support. Piretti discloses structure to provide lumbar support to the worker through the use of two separate backrest members that, like Adat et. al., employ a variety of adjustment mechanisms to provide the worker with desired back comfort. The adjustments in Piretti provide greater complexity to the worker using the chair and can allow the worker to adjust the chair backrest members to a less desirable ergonomic position. Additionally, in Piretti the added adjustment mechanism complexity adds to the overall cost and time required to manufacture and assemble the chair, making the design less feasible for mass production. Piretti has no teachings related to specific settings for the backrest in response to particular extended sitting fatigue problems experienced by the worker.
Continuing in the prior art, a chair having again two back support portions that are each independently adjustable is disclosed in U.S. Pat. No. 7,040,703 B2 to Sanchez. In Sanchez, separate back support members attach each chair back support to the seat of the chair. Such an arrangement in Sanchez only complicates the existing problem of adjustment complexity, as to adjust the back portions to the desired position to promote ergonomic support, there are an increasing number of adjustments that need to be made by the worker, thus increasing the time required to make the adjustments and increasing the difficulty in getting the chair back support positioned to a beneficial or desirable position. Moreover, Sanchez represents increasing complexity in the manufacturability and assembly of chairs leading to increased costs of production. Also as in Piretti, Sanchez has no disclosure of a method for selecting various adjustments to better accommodate chronic fatigue problem a worker has from extended periods of sitting.
Similarly, in U.S. Pat. No. 6,655,731 B2 to Martin disclosed is an adjustment mechanism that leads to complex adjustments and difficulty in replicating the desired position. In Martin, both the chair seat and chair back are adjustable rotationally about a parallel pair of axes of each the chair seat and chair back. The chair seat and chair back are also adjustable by adjusting the chair seat and chair back to various discrete adjustment positions that are provided along the horizontal and vertical members of the frame of the chair. While the arrangement in Martin does provide increasing versatility for a variety of workers, the limited adjustment ability leads to incorrect adjustments, as well as an inability to reproduce or replicate a desirable adjustment setting once the setting has been realized. Also, Martin lacks specific teaching as to how to set the various adjustments in accordance with the various worker ailments resulting from prolonged sitting periods.
Another common solution in the prior art is the use of a seat that may have a specific size or contour. While the use of a seat of a specific shape or size does not present the aforementioned problems of the adjustable back, the particularity of each shape may not be accommodating to all workers. This requires a plurality of designs or manufacturing techniques to accommodate different workers. In this respect, some prior art has sought to assist male or female genders through various differing forms specific to either male or female genders. While particularly shaped seats may alleviate some MSDs and other ailments related to the soft tissue of the posterior of the workers, the designs do not provide for any specialized support for the worker's back. Thus there is also a need to provide specifically designed chairs that accommodate gender specific anatomy, for instance, the anatomy of a woman's body. As the shape of a woman's body is unique, a chair design should similarly reflect and conform to the specific needs of women.
A prior art reference that discusses the need to use specific structure for chairs that differ with respect to men and women is in United States patent application publication number 2002/0175553 A1 to Steifensand. Steifensand discloses two species of chairs that differ based upon the gender of the worker. While Steifensand discloses a shorter seat for the female species of the chair, Steifensand fails to provide an adapted chair back for the female. Therefore, while Steifensand recognizes the need for specifically designed chairs for the differing body contours of the male and female worker, the invention in Steifensand falls short of adequately providing a chair back that is designed specifically for the female gender.
Similarly, in U.S. Pat. No. 5,110,183 to Jeanes, III teaches how the different anatomy of female and male genders effect the proper design of chairs. Jeanes, III uses tables of data compiled to represent the respective anatomies of males and females. Additionally, Jeanes, III discloses that a shorter seat in the distance that is parallel to the femur bone is preferable to a longer seat for the anatomy of a female. However, Jeanes, III attempts to solve the problem of discomfort for the infirm or persons confined to a wheelchair; therefore, Jeanes, III does not disclose a desirable position of the back of a worker that is performing tasks. Jeanes, III provides a chair that is suited for reclining or converting to a prone position. Thus, Jeanes, III is not feasible for a worker that is required to perform tasks. Moreover, Jeanes, III teaches away from using any contour of the seat or back, but instead teaches of using a flat, planar surface for both the back and seat portions of the chair. Jeanes, III also fails to provide a specific back to seat relationship desirable to promote correct ergonomics.
Next in U.S. Pat. No. 6,193,313 B1 to Jonsson provides a unique seat structure that predisposes the worker to a position in which the legs, hips, and back are aligned in a particular way. However, Jonsson teaches that it is desirable to pivot the worker's hips toward the chair backrest such that the worker's back is driven positionally into the lumbar support of the chair. Jonsson accomplishes this position by the structure of the seat alone. The invention in Jonsson tends to create a position that leads to a slouching posture where the top of the worker's spine is arched so that the worker's shoulders are positioned forward of the hips of the worker creating a position that leads to fatigue. In addition the posture Jonsson induces may promote discomfort in the lower portion of the worker's back.
Another prior art example of the use of contour to provide ergonomic support comes in U.S. Pat. No. 7,077,469 B2 to Badia i Farre that includes a seat surface designed to be straddled by the worker such that the legs of the worker are positioned so that the worker's legs are disposed on opposite sides of the seat. Additionally, Badia i Farre incorporates voids in the seating surface to accommodate the male genitals of the worker to prevent soft tissue contact with the seat. Again, due to the unconventional method of straddling the seat, a worker may not feel comfortable with using the Badia i Farre seat. Additionally, workers that use the design in Badia i Farre may find it difficult to mount and dismount the seat. Further, especially for women, the wearing of a dress as opposed to slacks would preclude the use of this straddling of the seat.
Other prior art solutions take on unconventional designs that position workers in fundamentally different positions than a traditional chair. One such position includes providing ventral support to the worker. These designs can lead to complexity and difficulty in use, especially when the worker mounts or dismounts the chair. As an example the following prior art references use either dorsal or ventral support structures to help induce correct ergonomic position. One such reference is U.S. Pat. No. 4,650,249 to Serber. Serber discloses an office chair that uses a ventral support in combination with a seat to help induce correct ergonomic position. However, in Serber such an arrangement where ventral support is used, the positioning of the support can lead to interference with the work task movements performed by the worker, as well as difficulty sitting on the chair and returning to a standing position. However, this type of office chair design being introduced decades ago has not meet with much market acceptance most likely due to the difficulty of the worker mounting and dismounting the chair, the lack of seating position flexibility, and the potential interference of the chair with desks and other office equipment. These problems are also present in U.S. Pat. No. 7,104,606 B2 to Congleton et. al. Congleton et. al. discloses a chair that is convertible from ventral to dorsal support. Again, in Congleton et. al. when in the dorsal support arrangement, the seat and back do not properly orient the hips of the worker and when in the ventral support arrangement, the issues of sitting and standing from the chair arise, much like in Serber.
Similarly, U.S. Pat. No. 7,090,303 B2 to Kropa discloses a chair that supports the worker ventrally by providing a rest that contacts the worker's abdomen and allows the worker to perform tasks in front of the worker. The primary problem Kropa addresses is the ability to rehabilitate lower leg injuries while seating through the use of abductor and adductor type movement attachments that allow the legs to be exercised while seated. However, in Kropa again, the design presents challenges for using the chair in that worker mounting and dismounting the chair becomes awkward with the addition of the abductor and adductor type movement extensions. Also, due to the ventral support of the worker in Kropa, the design may limit the number of workers willing or able to use such a design, especially as related to limitations to use of the workers hands and arms. Again, Kropa does not teach a method of setting adjustments in response to worker fatigue stemming from extended periods of sitting.
There exists a need to provide a chair that assists in positioning a worker in a manner that promotes prevention of MSDs, other related ailments, and reduces fatigue by utilizing the shape of the seat and back in addition to the position of the seat and/or back with respect to each other. Such a chair should be simple and inexpensive to produce and use without excess adjustability that adds complexity to the overall design. Such a design should also accommodate the varying sizes of workers, yet also be able to serve a large portion of the working population effectively, without drastic changes in the design or use of the chair. One such solution to the dichotomy of providing a chair to serve a specific shape, yet also be useful to a large population of workers may be to provide a chair designed especially for the unique anatomy of the female gender. The design of a female specific chair would allow for a large population of workers to be accommodated, while still tailoring the chair to the specific needs that a female anatomy presents. Additionally, to further assist in the reduction of MSDs, related ailments, and fatigue, it is desirable to perform a series of tests to determine what position is most desirable for a worker to take while working for an extended duration of time. Such tests should focus on the ability to reduce fatigue, and seek to determine the optimal position to provide ergonomic support to a worker. An objective measure for fatigue should be developed to accurately measure what size and relative position should be realized in the seat and back to accommodate a worker. Also, to overcome the problems in the prior art of common workers having difficulty in adjusting a chair into a desirable position, a method should be developed whereby a worker can properly and simply adjust a chair into the optimal position by following steps to properly orient the workers body prior to extended durations of time.